PANAMA CITY, PANAMA — Gen. Manuel Antonio Noriega's forces took the hardest line yet against political opposition Monday, snuffing out a protest of thousands of Panamanians literally in minutes and storming a major hotel to arrest opposition leaders and scatter foreign journalists.

In a development apparently influenced by the government's use of heightened force, the top church official of this largely Roman Catholic nation, Monsignor Marco Antonio McGrath, was expected to call today for Noriega to leave Panama, sources said late Monday.

The unprecedented storming of the Marriott Cesar Park Hotel in downtown Panama City came just after 6 p.m. as members of the anti-Noriega National Civic Crusade prepared to hold a press conference about the street demonstrations earlier in the afternoon.

In those demonstrations, 5,000 or more Panamanians calling for Noriega to resign were scattered by well-disciplined riot police, who attacked suddenly with water cannon, tear gas and birdshot. Leaders of the Crusade, a coalition of professional, business and private groups, seemed surprised by the stunning efficiency of the police action, which left no opportunity for the rock throwing and building of street barricades that have followed other demonstrations.

Before the press conference could begin, military, police and paramilitary forces surrounded the Marriott, the largest international hotel in the capital city. Witnesses said two unidentified men were forced into a van just outside the hotel's front doors. When others protested, a band of uniformed and civilian-dressed gunmen stormed into the lobby of the hotel, the witnesses said. The men carried shotguns, M-16s and Uzi machine guns.

Reporters and photographers of the foreign press and about 100 members of the Crusade scattered, running up stairways and to elevators. Gunmen blocked exits.

It appeared that there were nearly 50 people taken into custody, including a dozen journalists. The tapes and equipment of television crews were seized, and at least one American newspaper reporter was beaten.

A U.S. Embassy official put the number of people known to be missing from the hotel at eight: two Mexican employees of NBC television news, two ABC employees, a cameraman from CBS and three other journalists whose affiliations were not known. Other witnesses said journalists arriving at the scene in taxis also were pushed into army trucks.

Late Monday sources within the opposition said as many as 20 Crusade members were held at the Defense Forces headquarters. They said the journalists were released, but that three were taken into hospitals.

The gunmen searched the hotel room to room, although Crusade members managed to hide in the rooms, some with reporters. The hotel's telephone service was cut off for about two hours.

Hiding in a reporter's room at midevening was Crusade leader Aurelio Barrea. He said the storming of the hotel would be taken as not only a hardening of Noriega's position against opposition but also evidence ''that he's desperate and close to collapse.''

Barrea said that among the Crusade leaders arrested by the gunmen were Carlos Gonzalez De La Lastra, a top Crusade spokesman and protest organizer; Alberto Aleman, president of the Panamanian construction association; Frank Morrice, former president of the insurance association; and Luis Guillermo Casco Arias and Rodrigo Arosemena, leaders of the opposition Molirena Party.

Barrea said he and several other opposition leaders had planned to keep an appointment with Archbishop McGrath after the press conference to discuss a request Monday from Costa Rican President Oscar Arias and Prime Minister Felipe Gonzalez of Spain that McGrath mediate in talks between Noriega and those seeking to remove him as de facto ruler.

There had been speculation last weekend that Noriega might meet with Arias and Gonzalez in Costa Rica about resigning peacefully and going to Spain. Late Monday there were reports that those talks might have been a ploy to lure Noriega to Costa Rica, from which he could be extradited to the United States on drug charges.

Gonzalez said at a press conference Monday in San Jose that an ''immediate solution is necessary to end the anguish and the pain of the Panamanian people, and we believe that if Archbishop McGrath agrees to mediate, it would be a very important point.''

McGrath later told Crusade leaders he would take part in talks only if the opposition agreed to meet with Noriega. The opposition's position has been that it would negotiate with Noriega only if it had been determined beforehand that he was going to leave in ''an immediate situation'' and that the talks were simply for the details of the departure.